1. Field of the Invention
This invention relates to a cation exchange capacity titration unit and a method of determining the cation exchange capacity of drilled solids. More particularly, an automated cation exchange capacity titration unit and a method of determining the cation exchange capacity of drilled solids using the automated cation exchange capacity titration unit described herein.
2. Background Art
The cation exchange capacity of a drilling fluid, also referred to in the art as the methylene blue capacity, is an important consideration when drilling and/or servicing a well. The cation exchange capacity of a drilling fluid is typically determined utilizing a titration method similar to method API 13B-1 or equivalent. The cation exchange capacity of a drilling fluid is an indication of the amount of reactive clays (e.g., bentonite and/or drill solids) present as determined by the methylene blue test. The methylene blue capacity provides an estimate of the total cation exchange capacity of the drilling fluid solids. Methylene blue capacity and cation exchange capacity may not necessarily be equivalent, the former normally being somewhat less than the actual cation exchange capacity.
To determine the methylene blue capacity of a sample, a methylene blue solution is added to a sample of drilled solids which has first been treated with hydrogen peroxide and acidified to remove organic matter. The sample is titrated with methylene blue until the sample suspension is saturated with methylene blue, as determined by the presence of a dye ‘halo’ around a drop of the titrated suspension placed on a piece of filter paper. Variations of the procedure may be used on drill solids and/or on samples of commercial bentonite and/or other clays to allow an estimate of the amount of each type of solid present in a particular fluid.
However, this procedure is time intensive and the results may be operator dependent. A need exists for determining the cation exchange capacity of a sample in a more automated way, wherein the results are less subjective than allowed for utilizing the methods currently known in the art.